The present invention relates to an information recording and reproducing apparatus and, more particularly, to an optical disk apparatus and a track format on an optical disk medium which is used in such an apparatus.
As a kind of external memory apparatus in an information processing system or the like, for instance, an optical disk apparatus for optically recording/ reproducing information onto/from the surface of an optical disk as an information recording medium by irradiation of a laser spot or the like has been put into practical use as disclosed in the literature such as "Optical disk file apparatus of a large capacity in which code information became possible", Nikkei Electronics, pages 189 to 213, Nikkei BP Co., Ltd., Nov. 21, 1983, or the like.
As also disclosed in the above literature, in the optical disk, a possibility such that data errors occur is generally high as compared with the case of recording information to other recording media such as a magnetic disk. As a countermeasure for the occurrence of errors, a verification, that is, a read after write operation (hereinafter, referred to as an RAW operation) is executed by a method whereby just after information was written to the optical disk, the information is read out of the optical disk and collated with the information before it is written. Further, together with a plurality of user's sectors into which ordinary information is recorded, a predetermined number of alternating sectors are provided every track. When errors were detected in a user's sector by the RAW operation upon recording, similar original information is properly recorded into an alternating sector in the relevant track. Upon reproduction, the data in the user's sector having the errors is replaced by the data in the corresponding alternating sector.
Therefore, in the recording and reproducing operation of the information for the optical disk, a proper control including the RAW operation and the access to the alternating sector is inevitable. In the above literature, the multiplex recording and reproducing operations using a buffer memory are executed to realize ideal recording/reproducing operations such that the recording of the data of one track including the RAW operation is executed for a period of time of two rotations of the optical disk in the recording mode and that the reading-out operation of the data of one track is executed for a period of time of one rotation of the optical disk in the reproducing mode.
A flowchart for the multiplex recording and reproducing operations has been disclosed at page 209 in the above literature and is shown in FIG. 10.
That is, as shown in FIG. 10, the number of sectors included in one track is set to 64. Among them, the number of user's sector is set to 62 and the number of alternating sectors is set to 2. On the other hand, two buffer memories each having a memory capacity of one track are provided. Transmission and reception of data with an upper system are executed through the buffer memories in accordance with a data transfer of on the upper apparatus.
The data from the upper apparatus is first stored into the buffer memory (T.sub.1 in the diagram). The data in the buffer memory is recorded to a target track on the optical disk (W.sub.1 in the diagram). A laser spot is jumped to the adjacent inside track in the first alternating sector in the rear portion of the track (such an operation is called a sector jump) J.sub.1 in the diagram). Further, the recording data is verified by the RAW operation in the next rotation (R.sub.1 ' in the diagram). At this time, if the number of sectors which were determined to be unusable because of errors is one or less, the data to be written into the unusable sector is written into the second alternating sector in the relevant track. Subsequently, data T.sub.2 is written to the next track (W.sub.2 in the diagram). The laser spot is jumped to the adjacent inside track in the first alternating sector in the rear portion of the track (J.sub.2 in the diagram). The RAW operation to the alternating sector of the preceding track and the RAW operation for the writing W.sub.2 to the relevant track are executed (R.sub.2 ' in the diagram).
As mentioned above, if the occurrence rate of the erroneous sectors, i.e., alternating sectors in each track is equal to one sector/track, data of one track can be written by two rotations of the optical disk.
On the other hand, upon reproduction of data, the replacement of the data corresponding to the erroneous sector by the data of the alternating sector in the buffer memory can be executed without waiting for the rotation.
In the case of the above conventional technique, a condition such that the laser spot can be jumped to the track on the inner rim side within a desired passing time of one sector in the peripheral direction of the laser spot is used as a prerequisite.
However, there is a tendency such that the desired passing time of one sector by the laser spot is reduced by the improvement of the frequency characteristics of the recording/reproducing system or the like having an object to realize a high recording/reproducing speed of data or the like. On the other hand, in the present situation, a time of about 1 msec is required for the moving operation between tracks in the radial direction of the laser spot because such a moving operation ordinarily includes a mechanical operation.
Therefore, if the high recording/reproducing speed of data is improved and a desired passing time of one sector of the laser spot is shorter than the time which is required for the movement (track jump) between the adjacent tracks, in the case of the above conventional technique, there is a problem such that even if the error occurrence rate is equal to or less than one sector per track, it is impossible to realize the ideal writing operation such the data of one track is written for a period of time corresponding to two rotations of the optical disk including the RAW operation.